CVE-2026-86351
Received Received - Intake

Open Redirect Vulnerability in MISP Homepage Setting

Publication date: 2026-09-07

Last updated on: 2026-09-07

Assigner: CIRCL

Description
Affected versions of MISP validate the user-configurable homepage by checking only whether the supplied path begins with /. That check is insufficient because protocol-relative URLs such as //attacker.example also begin with / but resolve to an external origin in browsers. The vulnerable homepage value can be stored as a user setting and later used by the post-login routing logic. The commit explicitly identifies //attacker.example as a payload that passed validation and was emitted to the Location header after login. The fix introduces a shared InternalRedirectValidator that rejects URLs containing a host, scheme, userinfo, unsafe leading // or /\, malformed URLs, and control characters. It also revalidates homepage settings on read so legacy or internally written unsafe values cannot bypass the new storage-time validation. Version affected: ≤2.5.45

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Meta Information

Published
2026-09-07
Last Modified
2026-09-07
Generated
2026-09-07
AI Q&A
2026-09-07
EPSS Evaluated
N/A
NVD
CVE-2026-86351
EUVD
EUVD-2026-72343

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
misp misp to 2.5.45 (inc)
misp misp to 2.5.45 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-601 The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.
CWE-20 The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

Attack-Flow Graph

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Executive Summary

This vulnerability in MISP allows open redirect attacks due to insufficient validation of user-configurable homepage paths. The system only checks if the path starts with /, which is inadequate because protocol-relative URLs like //attacker.example also start with / but redirect to external origins. This bypasses security controls and enables attackers to redirect users to malicious sites after login.

Detection Guidance

Check MISP logs for post-login redirects to external domains. Inspect UserSetting.php and related files for homepage values containing protocol-relative URLs like //attacker.example. Use grep to search for 'Location: http' headers in web server logs after login attempts.

Impact Analysis

An attacker could trick users into clicking a malicious link that, after login, redirects them to a phishing or malware site. This could lead to credential theft, session hijacking, or installation of malicious software. Users with access to MISP may unknowingly expose sensitive data or compromise their systems.

Compliance Impact

This vulnerability could violate data protection requirements under GDPR and HIPAA by enabling unauthorized redirection to external sites, potentially exposing user data or credentials. Organizations using affected MISP versions may fail compliance audits if they do not address this open redirect issue promptly.

Mitigation Strategies

Upgrade MISP to version 2.5.46 or later. Review and update homepage settings to remove any protocol-relative URLs. Implement the InternalRedirectValidator in all user-controlled navigation paths. Monitor for unauthorized redirects in web server logs.

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